1. Field of the Invention
This invention generally relates to diving equipment and more particularly to the viewing lens of the equipment that is being used by the diver to view objects in the water around them.
2. Description of the Related Art
Typical diving equipment that is used to view objects underwater is usually in the form of a mask (nose and eyes), full face mask (mouth, nose, and eyes), or helmet (entire head). Masks and full face masks generally have a soft seal that conforms to the divers face and has a viewing lens which consists of transparent window(s).
A flat single pane lens must be used in front of the diver's two eyes at every point that both eyes can see through. If there are two or more panes that both eyes can see through, an additional image will be seen. Two panes will result in two images that the visual center of the brain has difficulty making sense of. This can result in nausea and dizziness. A curved lens will result in each eye looking through a different part of the curve. This also results in visual confusion, nausea and dizziness.
Optically correct lenses have been designed and manufactured but with little or no acceptance. All divers have learned to dive viewing through a flat, single pane lens. Once acclimated to the flat lens the corrected lens appears to be abnormal and confusing. Additionally, the corrected lens for underwater is out of focus in the air. This leaves the diver on the surface no choice but to remove the masks for vision requirements out of the water.
Divers have been taught that underwater objects appear to be only three-quarters as far away as their physical distance. For objects subtending small angles at the mask and eye it is true that, for any object distance, the objects in water virtual image produced by the air-water interface (lens) is always nearly 25% closer to the interface. This results in most objects appearing to be 25% closer to the relatively new diver. This is a consequence of the laws of refraction, sometimes referred to as “Snell's Law,” as depicted in FIG. 1. Experience and acclimation can help overcome some of this perceived view.
The divers' vision is also limited by the size, shape and location of the viewing lens. Past attempts at improving the vision of the diver, especially peripheral vision, have mostly consisted of adding additional windows. For example, U.S. Pat. No. 5,345,615 discloses adding downward facing “pectoral region” windows to provide a degree of downward visibility. Most manufacturers also try to position the lens as close to the eyes as possible to help minimize the effects of refraction and to improve the visual field. See also U.S. Pat. No. 3,671,976 which teaches a frontal planar section with adjacent curved portions.
One of the problems with the current masks that have side windows is that the side windows are at too great of an angle (70° to 90°) when compared to the forward facing window. The results of this are, for example, that when the diver is observing an object that is moving from a side window to a front window or visa versa, especially when the object is more than 6″ from the mask, the object disappears or partially disappears from the side window then reappears in the front window, creating a missing part of the total view between the two windows or a blind spot. The greater the angle the windows are to each other the more of the view between the windows is lost. In addition, the diver's eyes have difficulty focusing at these lateral angles so the visual information is limited.
Another problem with visibility is that a blind spot is also created by the plastic bar between windows in prior art masks. Recent attempts at removing this plastic bar between the windows have included that disclosed in Published Application U.S. 2002/0005931 A1, that discloses a mask where the windows are fashioned in such a manner that the sides and front windows are bonded together with a flexible glue, then molded into a plastic frame. The glue joint between the pieces of glass are cut and ground in a way that only a very thin line is visible to the user of the mask, similar to the early aviator's goggles, eliminating the plastic bar between the windows. This helps greatly out of the water. But underwater, because the windows are flat pieces of glass with cut and ground edges that are glued together, this creates an immediate and abrupt change in angles between the pieces of glass, and the blind spot remains, as depicted in FIG. 2.